A history lesson can happen anywhere. Even in motion. And even when riding the slow-motion Portland Streetcar.

The 8-mile loop is, in one sense, an oh-so-relaxed, car-free way to get around Portland's urban center. But for the price of a fare, streetcar riders get much more than a commute.

Stop checking messages on your smartphone and look out the window -- you'll witness a fascinating visual history of Portland's architecture and urban development in the past two decades.

A round trip offers, for example, views of leafy Northwest Portland, the hippest part of town in the 1990s; the grit and polish of the city's downtown core; the sterile but seductive South Waterfront; and the well-crafted condos of the Pearl District, nationally recognized for its posh, mixed-use developments.